Runcible was a presenter of Gallifreyan Public Video, essentially that planet's equivalent of a TV news reporter. His rather pompous personality earned him the nickname Runcible the Fatuous.
He knew the Doctor well-enough to recognise him even after several regenerations, but could not recall the exact circumstances which led to his initial departure from Gallifrey.
Runcible's recording of the assassination of the Time Lord President could have cleared the Doctor and revealed the identity of the actual killer, and so the Master stole the tapes and murdered both Runcible and his cameraman. The cameraman was killed with the TCE and his shrunken corpse left within the camera, while Runcible was simply stabbed in the back. (DW: The Deadly Assassin)
There is no reference to the possibility of Runcible regenerating, even though this is a fairly mundane injury by Time Lord standards. Runcible therefore was not a Time Lord or was at the end of his regenerative cycle, either of which would be curious given he is presented as a contemporary of the Doctor.